Single stage amplifier-detectoramplifier



March 12, 1957 .1. G. SPRACKLEN SINGLE STAGE AMFLFIER-DETECTOR-AMPLIFIER.'5 Sheeis-Sheet l Filed Aug. 22, 1952 JOHN G. SPRACKLEN IN V EN TOR.

HIS ATTORNEY March 12, 1957 1 G. SFRACKLEN 2,785,299

SINGLE STAGE ANPI..F'IEP-DETECTOR-AIVIPLIFIER Filed Aug. 22, 1952 5Shee'ts-Sheet 2 F/QZ l l I l I l I I I I I l .I

l I I- JOHN G. SPRACKLEN INVENTOR.

HIS ATTORNEY 3 Sheets-Sheet 5 Filed Aug. 22, 1952 HIS ATTORNEY.

United States Patent John G. Spracklen, Chicago, Ill., assignerCorporation, a corporation oi' Appii'cation August 22, 1952, Serial No.365,875

12 Claims. (Cl. 25u- 259)- Sodio This invention relates to Wave-signaltranslating apparatus and more particularly to such apparatus which isparticularly adapted to amplification and demodulation of modulatedWave-signals. This application is a continuation-impart of copendingapplication Serial No. 154,089, filed March 29, 195i), now abandoned,for Wave-Signal Translating Apparatus, and assigned to the presentassignee.

in the reception of modulated wave-signals, it is convcntionai practiceto heterodyne the incoming radio-frequency signal with alocally-generated constant-frequency signal to provide a modulatedintermediate-frequency signal. The modulated intermediate-frequencysignal is amplied and demodulated to provide an audio-frequency orvideo-frequency signal representing the modulation components of theoriginal wave-signal, and the detected signal thus obtained is ampliliedand applied to a suitable utilization device such as a loudspeaker or animagereproducing device. Conventionally, several cas-:aded stages areutilized to provide the desired intermediate-frequency amplification,and separate independent stages are ordinarily used to eect demodulationand subsequent amplilication of the modulation components. Thus, forexample, in a conventional television receiver, four cascaded stages ofintermediate-frequency amplilication may be used, followed by arectifier device for Video-frequency demodulation and two cascadedstages of video-frequency ampiification.

lt is an important object of the present invention to provide novel andimproved Wave-signal translating apparatus for providing in a singlestage ampliiication of both a modulated Wave-signal and the modulationcomponents of such amplied signal after demodulation.

t is a further object of the invention to provide improved Wave-signaltranslating apparatus for combining in a single stage the functions ofmodulated wave-signal amplification, demodulation, and subsequentamplitication of the modulation components.

Still another object of the invention is to provide new and improvedwave-signal translating apparatus for combining in a single stage thefunctions of two or more separate and independent stages of conventionalwavesignal receivers, thereby eecting a substantial cost saving inreceiver manufacture.

ln accordance with the invention, the above and other objects areachieved by providing an electron-discharge device including in theorder named, a cathode, a iirst control grid, an accelerating electrode,a second control grid, and an output electrode. An input circuit isprovided for impressing an amplitude-modulated Wave-signal, having apredetermined carrier frequency, between one of the control grids andthe cathode. There is also provided a circuit from the other controlgrid to the cathode including a resonant two-terminal load circ-uithaving one terminal coupled externally of the electron-dis- Chargedevice to the other control grid only and having Frice an impedance atthe input-signal frequency which is greater than the reciprocal of theeiiective transconductance, at the input-signal frequency, of the inputcontrol grid With respect to the other control grid for developing anamplified replica of the modulated input-signal. Means are coupled tothe other control grid and to the cathode for efecting' separation ofthe modulation components tire amplified modulated wave-signal and forsubstantially modulating the electron iiow to the output electrode inaccordance with the modulation components of the arnpliied input-signalreplica. Means, in cluding an output load circuit coupled to the outputelectrede and to the cathode for utilizing the transconductance of theother control grid with respect to the output electrode, are providedfor amplifying the modulation components.

ln accordance with another feature of the invention as adapted to atelevision receiver, an intercarrier-frequency circuit, tuned to afrequency corresponding to the frequency dierence between thevideo-carrier and soundcarrier components of the input compositetelevision signals, is included in the output circuit either in additionto or in place of the video-frequency load circuit.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The invention,together with further objects and advantages thereof, may best beunderstood, however, by reference to the following description taken inconnection with the accompanying drawings, in the several gures of whichlike reference numerals indicate like eiements, and in which:

Figure 1 is a schematic diagram of a television receiver embodying novelwave-signal translating apparatus constructed in accordance with thepresent invention;

Figures 2, 3, and 4 are schematic diagrams of other embodiments of theinvention, and

Figure 5 is a schematic diagrampof a television receiver utilizingcertain principles of the present invention.

In Figure l, incoming composite television signals are intercepted by anantenna 10 and impressed on a radiofrequency amplifier 11 consisting ofone or more stages. Amplilied composite television signals fromradio-frequency ampliier 1i are heterodyned with locally-generatedconstant-frequency oscillations in an oscillatorconverter 12 to providean intermediate-frequency signal which is applied to anyintermediate-frequency amplilier 13 consisting of one or more stages.The amplified intermediate-frequency composite television signal fromintermediate-frequency amplifier 13 is impressed upon Wave-signaltranslating apparatus 14, constructed in accordance with the invention,for further intermediatefrequency amplification, demodulation, andamplification of the modulation components in a manner to be hereinafterdescribed.

Detected and amplified video-frequency components from wave-signaltranslating apparatus 14 are applied to a second video-frequency amplier15 and thence to the input circuit of a cathode-ray tube 16 or otherimage-.reproducing device.

The receiver schematically illustrated in Figure l is of theintercarrier sound type which, per se, is well known in the art.Wave-signal translating apparatus 14 is Constructed and arranged toprovide an intercarrier sound signal which is applied to an intercarrieramplifier 17. The amplified intercarrier sound signal from amplilier 17is amplitude-limited and demodulated in a limiter-discriminator 18, andthe audio-frequency output from limiter-discriminator 18 is impressed onIa power amplilier 19 and thence on a loudspeaker 20 or `othersoundreproducing device.

, The detected and amplied composite video signal from wave-signaltranslating apparatus i4 is also applied to a synchronizing-signalseparator 2E. which operates to derive line-frequency andiield-frequency synchronizing-signal pulses for driving the scanningapparatus associated with image-reproducing device 1d. Field-frequencysynchronizing-signal pulses from synchronizing-signal separator 2l aresupplied to a field-frequency scanning-signal generator ZZ which drivesYa field-frequency scanning coil 23 associated with image-reproducingdevice lo. Linefrequency synchronizing-signal pulses from synch;ing-signal separator 2l are applied to an automatic-frequency-control(AFC) phase-detector 2li for phase cornparison with the output of aline-frequency scanning-signal generatorZS. The output of AFCphase-detector 24 is supplied to a reactance tube 26 which operates tocontrol the frequency of generator 25 to maintain chronism with theincomingsignal. The output of linefrequency scanning-signal generator 25is supplied to a line-frequency deflection coil 27 associated withimage-reproducing device 16 in a conventional manner.

With the exception of wave-signal translating apparatus i4, theconstruction and operation of the receiver of Fig- ,ure l are quiteconventional. it has been found convenient to illustrate a receiver ofthe intercarrier sound type since the invention is of particularadvantage as applied to such receivers, but it is to be clearlyunderstood that the invention may be applied with advantage to receiversutilizing a separate sound channel or other type of sound system.

More particularly, wave-signal translating apparatus 14, which performsthe several functions of intermediate-frequency amplification,video-frequency demodulation, intercarrier-sound detection, andvideo-frequency and intercarrier-frequency amplification, comprises anelectrondischarge device 3i? having in the order named, a cathode 31, aiirst control grid 32, van accelerating Velectro-de 3 which mayconveniently be formed as a screen grid, a second control grid 34, andan output electrode or anoce 35. if desired, device 30 may also comprisea screen grid 36 and a suppressor grid 37 between. second control grid34 and output electrode 35. r,The cathode 31 of device 30 is directlyconnected to ground, and accelerating electrodes 33 and 35 are connectedthrough a decoupling resistor 3Q to the positive terminal of a suitablesource of unidirectional operating potential, here shown as a battery38, the negative terminal of which is grounded. Accelerating electrodes33 and 36 are bypassed to ground by means of a condenser di). Suppressorgrid 37 is directly connected to cathode 31.

The intermediate-frequency signal from ampliier is impressed betweeniirst control grid 32 and cathode 3l, by means of an input circuitcomprising a coupling con-- denser 4i and a grid resistor 4t2. Asuitable source of negative unidirectional operating potential, hereshow as a battery 43, may be included in the direct-current return pathfrom control grid 32 to cathode 31 to provide a suitable operating biasfor control grid 32.

There is also provided a circuit from second control grid 34 to cathode3l, through ground, which includes two-terminal load circuit 4d. Loadcircuit 44 consists essentially of an inductor d5 which is coupled inparallel with the interelectrode capacity 46 between second control grid34 and cathode 31 by means of a small condenser 47 connected in Serieswith a large condenser 48. One terminal of load circuit 4d is coupledexternally of device 3i) to control grid 34 only.

The circuit from second control grid 3e to cathode 3i. `also includes arectifier device 49, such as a crystal, diode, or other unilaterallyconductive device, which is connected to control grid 34 directly and toground through 'condenser A resistor 58 is connected in parallel withcondenser 47 to constitute therewith a passive load net work forrectifier device d?. Suitable operating biasV potential for secondcontrol grid 34 is provided by means assenso of a battery 5l. or othersuitable potential source, the positive terminal of which is groundedand the negative terminal of which is coupled to the low-potentialterminal 51?, of coil 45 by means of a decoupling resistor 53.

Suitable positive unidirectional operating potential is supplied tooutput electrode 35 from a battery 54 or other operating potentialsource through a video-frequency load impedance comprising a resistor 55and a peaking coil S6, and through a parallel-resonant circuit 57comprising the primary winding 53 of a transformer S9 'and a condenserCircuit 57 is tuned to the intercarrier frequency, and the secondarywinding 6l of transformer 59 is coupled to intercarrier amplilier 17.Battery 54 is bypassed to ground by means of a condenser 62.

The detected and amplified video-frequency signal ap- /ideo amplifier i5by means of lead 63 and to synchroni -signal separator 21 by means oflead 64.

iriey, wave-signal translating apparatus i4 serves to provideintermediate-frequency amplication, video-frequency demodulation,intercarrier-sound detection, and iuteicairier-frequency andvideo-frequency amplification. The intermediate-frequency signalimpressed on irst control giid 32 is amplified by virtue of the spacecharge coupling from first control grid 32 to second control grid 34?-,and an amplified replica of the intermediate-frequency input signalappears across load circuit d4. Rectifier device 49 and its associatedload network comprising resister 59 and condenser 47 operate todemodulate the aniplied replica of the modulated inputsignal and toimpress the demodulated signal on control grid 34. This detected signalappears in ampliiied form across resistor 55 and peaking coil 55 byvirtue of the transconductance of second control grid 3d with respect tooutput electrode 3S. The video-carrier and audio-modulatedv soundcarriercomponents of the amplied signal developed at second control grid 34 arealso intermodulated by rectiiier i9 to produce an audio-modulatedintercarrier sound signal which appears inamplied form across tunedcircuit 57.

More particularly, it is known in the art that whenever a low-potentialcontrol grid is placed in the path of an electron stream in a positionfollowing a high-potential accelerating electrode, a virtual cathode .isproduced in the vicinity of the control grid. As the intensity of theelectron `stream projected through the accelerating electrode is variedin accordance with an input signal, the charge density of the virtualcathode is varied in a corresponding manner, and if a suitable inductiveload is connected to the low-potential control grid, an amplifiedreplica of the input signal is induced at the control grid by spacecharge coupling from the input grid. This space charge coupling eifecthas been formaliy likened .to a unilateral negative capacity having amagnitude of the order of a few micro-microfarads. Because it isunllateral in nature, it may be considered as providing an eectivetransconductance from the input grid to the lowpotential control gridhaving a magnitude of 21rfC, where f is the input-signal frequency and Cis the equivalent space charge coupling capacity.

In order to provide intermediate-frequency amplification between rstcontrol grid 32 and second control grid 3d, therefore, the impedance oftwo-terminal load circuit d4 at the intermediate-frequency is madegreaterV than the lreciprocal of the eective transconductance, at theintermediate-frequency, of first control grid 32 with respect to secondcontrol grid Se. Since amplication may be computed as the product of theeective transconductance and the load impedance, as is well known in theart, amplification or gain greater than unity is thus achieved. Inpractice, ratios of load impedance to reciprocal effectivetransconductance much greater than unity are preferred; for example,ratios of 10 or more have been employed with eminent success.

In accordance with the invention, the Ycircuit from across resistor 5Sand peaking coil 56 is supplied Y second control grid 34 to cathode 3E.includes` a rectifier Adevice 49 and a passive load network thereforcornprising the parallel combination of resistor Si?, capacity 46, andcondenser 47. In order to provide video-frequency demodulation, the timeconstant of the rectifier load network is made short with respect to theperiod of the highest video-frequency component to be de tected, forreasons which are well known. The amplified replica of the input signalappearing across coil 45 is impressed across rectifier device 49 and itsassociated load circuit and is therefore demcdulated, the detectedsignal appearing across resisto-r Si? and condenser This detected signalis applied to second control 34 througdcoil 45 to modulate the electronflow to output electrode 35 in accordance with the modulationcomponents, and amplification of the detected signal is accomplished byvirtue of the transconductance of second control grid 34 with respect tooutput electro-de 35, which works into the load circuit comprisingresistor 55 and peaking coil 55. At the same time, the ampliiiedvideocarrier and sound-carrier components appearing at second controlgrid 34 are intermodulated by rectiiier e9 and thel resul' gintercarrier-frequency signals, bearing the vaudio inoculation, areamplified by virtue of the transconductance of ,second control grid 34with respect tov output electrode 35, working into tunedintercarrierfrequency load circuit 57. In this embodiment, battery Slisselected to bias second control grid 34 to a relativelylinear portion ofits dynamic transfer characteristic, to provide video-frequencyamplification with a minimum of distortion from tube characteristiccurvature.

*InA order to provide eliicient intermediate-frequency amplification ofthe wide-band picture signals, the several stages ofintermediate-frequency ampliiier 13 and load circuit 44 may bestagger-tuned in a manner well known in the art.

, Merely Yby way or" illustration, and in no sense by way of limitation,satisfactory operation of wave-signal translating apparatus 14 has beenobtained at an intermediatefrequency` of 45 megacycles with thefollowing circuit components:

Electron discharge device 353 Type 6BE6. Vve'crtiier device 49 Type 1N64crystal rectifier. Resistor 39 220 ohms. Resistor'42 19,900 ohms.Resistor 5l) 4,70() ohms. Resistor 53 l megohm. Resistor 4,79() ohms.Condenser 41 .001 microfarad. Condenser 47 l() micro-microfarads.Condenser 43 .O47 microfarad. Battery 38 1GO volts. Battery 43 1.5volts. Battery 51 1.5 Volts. Battery 5e 150 volts.

lnductor d is made of suitable size to resonate at theintermediate-frequency with the capacity of -the circuit from the secondcontrol grid to the cathode, comprising lnterelectrode capacity L55 andcondensers 47 and 48. In the embodiment of Figure l, it is of coursepossible to usea single cathode biasing network toprovide' operating;bias for control grids 32, and 34, in lieu of using separate biasbatteries 43 and 51. Comparison -of this circuitl with the combinationof a conventional singlestage intermediate-frequency amplifier andcrystal detector reveals that about 40%V greater detected outptitfmay beobtained by the circuit of the present invention.

r flicembodiment of Figure 2 is generally similar to that illustrated inFiguire l with the exception that d..- modulation of the ainpliedreplica of the intermediatefieduencyinputsignal is accomplished withoutthe use avcrystaldiode or other external rectifier device. Inthecircuit'f Figure 2, the rectifier device and its vassociated loadcircuit are omitted from the second control? 'grid-cathode circuit, andbiasV battery 51 is adjusted to bias second control grid 34 to anon-linear portion of its dynamic transfer characteristic. The amplifiedreplica of the input signal developed across two-terminal load circuit4d is impressed on second control grid 34 by virtue of the same circuitconnection by which it is developed, and derncdulation of the ampliiiedreplica is accomplished by anode-bend detection; in other words, sincesecond control grid 3d is biased to a non-linear' portion of its dynamictransfer characteristic, the electron flow to output electrode 34 issubstantially modulated in accordance with the modulation components ofthe amplified input-signal replica. intermodulation of the videocarrierand audio-modulated sound-carrier components, and ampliiication of theresulting intercarrier sound signais and the detected composite videosignals form secondl control grid 3d to output electrode 35 areaccomplished as before by virtue of the mixing action at the secondcontrol grid and the transconductance characteristic of the secondcontrol grid with respect to the output electrode.

lt is also possible, in accordance with the invention, to effectdemodulation of the amplified input-signal replica by other meansincluded in the second control gridcathode circuit and utilizing anoperating characteristic of the second control grid. For example, aresistancecapacitance circuit having an' appropriate time constant maybe included in the second control grid-cathode circuit, and the secondcontrol grid may be biased to a non-linear portion of its grid currentcharacteristic, so that demodulation of the amplified replica isaccomplished by grid leak detection.

While satisfactory operation of the circuits of Figures i and 2 has beenachieved, these circuits may exhibit a certain amount of instability dueto the relatively high bilateral interelectrode capacity between grids32 and 34, which may result in undesirable feedback from load circuit 44to input grid 32. In the circuit of Figure 3, these undesirable effectsare obviated by virtue of a special neutralizing circuit for providingdegenerative feedback from two-terminal load circuit 44 to input controlgrid 32.

ln Figure 3, the intermediate-frequency input signal from amplifier 13(Figure l) is applied across the primary winding of an input transformer7l, the secondary winding 724 of which is coupled between input controlgrid 32. arid grid resistor 42. The distributed capacity 73 betweeniirst control grid 32 and ground is shown in broken lines in thedrawing. A neutralizing condenser 74 is connected from a tap 75 near thelow-potential terminal of coil i5 to the low-potential terminal ofsecondary winding 72, and a second condenser 76 is connected from thelow-potential terminal of secondary winding 72 to ground. Alternatively,windings 7u and 72 of input transformer 7l may be bifilar windings toprovide a distributed capacity to ground equivalent to condenser 76. Therectifier load network comprising resistor 59 and condenser 47 is"connected between the high-potential terminal of coil 45 and secondcontrol grid 3e', in order to preclude feedback of the demodulatedsignal to the input grid.

ln the circuit of Figure 3, condensers 74 and 76, distributed capacity73, and the bilateral interelectrode capacity between control grids 32and 34 constitute the four legs of a capacitive bridge network. Bysuitably selecting the value of neutralizing condenser 74,'thedegenerativefeedback from two-terminal load circuit 44 to input Lcontrolgrid 32 may be made just suii'icient to neutralize the regenerativefeedback due to the bilateral interelectrode capacity between controlgrids 34 and 32.

In the circuit of Figure 1, -the'bandwidth' of the twoterminal loadcircuit 44 across which the ampliediuputsignal replica-.is-developed isdependent uponthedamping of that-circuit. A large part of this dampingis attributable to rectifier-device 49, and in some instances, this'damping may be excessive. As illustrated in Figure 4, rectifier device49 may be connected between a tap @d on coil 45 and condenser 4S toreduce the damping of load circuit 44 to such an extent as to obtain thedesired bandwidth.

Moreover, the obtainable input-frequency amplification with the circuitof Figure l is limited by the inclusion in the intermediate-frequencyreturn path from coil 45 to ground of rectifier load condenser 427,which must be maintained at a small value to reduce attenuation at thehigher video-frequencies and to make it possible to use a largerectifier load resistor 59. As shown in Figure 4, theintermediate-frequency impedance of the return path from coil d5 toground may be reduced by including va series-resonant circuit,comprising an inductor Si and a condenser 82, in parallel with rectifierload condenser e7, thereby to achieve increased intermediate-frequencyamplification from input control grid 32 to second control grid 34.Inductor 3f, and condenser 82 are tuned to the intermediate-frequency toprovide a zero-impedance shunt across condenser i7 for the amplifiedinput-signal replica.

Moreover, the capacity of con-denser di is reduced by an amount equal tothe capacity of condenser 82 to increase the selectivity of load circuitby enabling a larger rectifier load Vresistor titl to be employed. lnall other respects, the circuit of Figure 4 is identical to that ofFigure l.

In all of the embodiments of the invention thus far described, a singlemultigrid electron-discharge device has been employed to provideintermediate-frequency amplication, video demodulation, intercarriersound detection, and amplification of both the intercarrier soundsignals and the demodulated composite video signals. he invention mayalso be employed to advantage, however, in a television receiver inwhich the video and sound components of the intermediate-frequencycomposite television signals are detected in separate stages.

The television receiver illustrated in Figure 5 is specificallydescribed and claimed in a copending divisional application, Serial No.426,909, led April 5, 1954, for Wave-Signal Translating Apparatus, andassigned to the present assignee. in this instance, incoming compositetelevision signals received by an antenna @il are applied through aradio-frequency amplier $1 to an oscillatorconverter 92.intermediate-frequency composite television signals fromoscillator-converter 92 are applied to an int termediate-frequencyamplifier 93, which may consist for example of three or fourcascade-connected l. F. amplifier stages. Amplifier 93 is `coupled to avideo detector` 94, which may be of conventional construction, and thedetected composite video signals from detector 9d are amplied by a videoampliier 9d and applied to the input circuit of a cathode-ray tube 96 orother image-reproducing device. Composite video signals from vi-deoamplifier 95 are also applied to a synchronizing-signal separator 97,and the line-frequency and eid-frequency synchronizingpulse componentsfrom separator 97 are employed to control line-freouency andfield-frequency scanning systems 98 and 9 which, in turn, providesuitable scanning signals to line-frequency and field-frequency-deection coils 10d and 1531 respecively.

intermediate-frequency amplifier 93 is also coupled by means of outputcircuit ll to wave-signal translating apparatus 19d constructed inaccordance with the present invention, where the intermediate-frequencysignals are further amplified and the video-carrier and sound-carriercomponents are intermodulated and amplified to provide an amplifiedaudio-modulated intercarrier-frequency sound signal. This amplifiedintercarrier-sound signal is applied to a limiter-discriminator E65, andthe resulting audiofrequency signals, after amplification in audiocircuits 196, Vare impressed on `a loudspeaker 167 or othersoundreproducing device.

The receiver of Figure 5 may be of conventional construction with theexception oi wave-signal translating apparatus 1312.' Apparatus 'lilacomprises a single electrontil) discharge device 108 including in the.order named av cathode 1%9, a first control grid 11d, an acceleratingor screen grid 111, Va second control grid 112 and an output electrodeor anode lil- 3. An additional screen grid 114 and a suppressor gridi'may be provided between second control grid M2 and anode 313.

Intermediate-frequency composite television signals, includingvideo-carrier and audio-modulated sound-carrier components separated bya predetermined frequency difference, are applied between first controlgrid 1716 and cathode in? by means of a coil 116 magnetically coupled tooutput circuit 1%3 of intermediate-frequency amplifier g3'. Cathode M9is connected to ground through a circuit comprising a resistor il? and acondenser 118, `and screen grids 1li and 114 are connected together andthrough a resistor i213 to the positive terminal of a battery il? orother source ofY unidirectional operating potential, the negativeterminal or which Vis grounded. Screen grids 111 and 114i are alsobypassed to ground by means of condenser 123 Suppressor grid E15 isdirectly connected to ground.

A two-terminal load circuit, tuned to the receiver intermediatefrequency and comprising an inductor 122 and an effective shunt capacity123 which may be composed of distributed circuit and interelectrode tubecapacities, has one terminal 124 coupled externally of device 10S tosecond control grid H2 only, through the parallel combination of aresistor 125 and a condenser 126. A parallelresonant trap circuit 127tuned to the intermediate frequency of the receiver may also beinductively coupled to inductor E22. The other terminal 128 of the tw0-terminal `load circuit is coupled to cathode 109 through ground and thecathode bias circuit comprising resistor .i7 and condenser 11S.

Anode 113 is coupled to the positive terminal of a battery 1.29 or othersuitable source of unidirectional operating potential through anintercarrier-frequency load circuit comprising an inductor i3@ shuntedby an effective capacity 131 which may be composed of distributedcircuit capacities. Battery 129 is bypassed to ground by means of acondenser 132. Anode 113 is also coupled to limiter-discriminator iiiSby means of a lead 133.

in operation, intermediate-frequency composite video signals, includingvideo-carrier and audio-modulated sound-carrier components, areimpressed on rst control grid 11d. Inductor 122 and effective shuntcapacity 123 are tuned to the intermediate frequency, to provide animpedance at the frequencies of the carrier components greater than thereciprocal of the effective transconductance, at such frequencies, offirst control grid 110 with respect to second control grid i12.Consequently, the video-carrier and sound-carrier components appear inamplified form at second control grid 112 by virtue of space chargecoupling from first control grid 110 to second control grid 112. Trapcircuit 127, also tuned to the intermediate frequency, may be providedfor the purpose of emphasizing the carrier components by providing adouble-peaked impedance characteristic for the two-terminal load circuitcoupled to second control grid 112.

Second control grid 112 is biased to a non-linear portion of its dynamictransfer characteristic by means coupled to second control electrode 112and to cathode 199. in the illustrated embodiment, this operating biasis provided by cathode resistor 117 and condenser 118 and further byresistor 25 and condenser 126 connected in the return path from secondcontrol grid 112 to ground; however, it may be possible by judiciousdesign of the tube to operate second control grid 112 at zero bias, inwhich event the biasing means may consist of a direct connection betweenterminal 12S and cathode 109. Consequently, the video-carrier andaudio-modulated sound-carrier components of the amplified signalappearing at second control grid 112 are subjected to anodebenddetection and are intermodulated by device 108 to prnvide anaudio-modulated 'signal having a carrier freco1ijespondingY to the'frequency separation be'- tween'the video-carrier and sound-'carriercomponents. Load circuit 13`131 is tuned tothe intercarrier frequency,and amplilied'intercarrier soundr signals are developed atv anode 113Aby vvirtue of the transconductance characteristic of second control grid112 with respect to anode 113,.Y These intercarrier signals, bearing theaudio modulation, are applied to limiter-discriminator 105 where theyarek detected "to, provide audio-frequency sigpals which are applied,after suitable amplification, to loudspeaker 107.

Resistor 1 254 land condenser' 1,26, having a time constant which isshort with respect to the highest-audiofrequency components, arepreferably included in the circuitY from second control grid 112 tocathode 109. Resistor-condenser network 125, 126 provides an automaticvariation in the biasV of second control grid 112 in accordance with theaudio-frequency modulation components, thus tending to prevent theamplified intermediate-frequency signals from driving the second controlgrid beyond itsY linear operating range and thus avoiding undesirablemodulation of the intercarrier sound signals by changes in picturecarrier level in accordance with the video and synchronizing components.

In'all embodiments of the invention, ampliication of theVmodulatedcarrier input signals is accomplished by virtue` of Vspacecharge coupling between two control gridsvseparated by an acceleratingelectrode. In each case,`means associated with the second control gridare provided for effecting demodulation of the amplified replicaof theinput signal and for modulating the electron flow to the outputelectrode of the tube in accordance with modulation components of theampliiied replica. These modulation'components are then amplied byvirtue'of the transconductance of the second control grid with respecttothe nal anode or output electrode. lneither case, the post-detectiongain is proportional to the transconductance of the second control gridwith -respect to `the anode. However, in the embodiments employing aseparate rectier for detection, the overall conversion gain isproportional -to the transconductance or rst derivative of anode currentwith respect to second-control-grid voltage at'theV operating point,while in embodiments employing anode-bend detection at the secondYcontrol grid, the overall conversion gain is proportional to thefiirstderivative of that transconducta'nce. or second derivative of anodecurrent with respect to second-contr'ol-grid voltage, which is a measureoffz thefdegre of non-linearity of the dynamic transfer characteristicat the'operating point.

Thus, the invention provides new and improved wavesignal translatingapparatus "for effectively accomplishing ina single stageand severalfunctions of input-signal amplication, demodulation, and subsequentamplificationl of themodulation components. While the invention has beenshown, and described in the environment of atelevision receiver, it mayalso be used to advantage in other types of modulatedv wave-signaltranslating apparatussuch as ultra-high frequency amplitude-modulationreceivers. 'Howeven since the invention is dependent on the'`advantageous use of the spacecharge coupling eifect, which isjof usefulmagnitude only at relatively high frequncies, its utility` is limited toapplications at frencies'of the` order of l megacycle or higher."Whilefpa'rticular embodiments of the present invention havebeen shownyandrdescribed, it is apparent that numferous; variations andmodifications may be made, and iti is therefore contemplatedein theappended claims to cover all such variations and modificationsV as fallWithin the true s'pirit'apdf scope of the invention.

"l claimz' 1. Wayesignal translating apparatus comprising: anelectron-discharge',deyiceincluding, in the order named, an cathode,awfirst' control grid, an accelerating electrode,

a. Second Control. grid, and an Qutpufeletrods; ,2.1.1.1. inputcirc:i.`1i't"`forV impressing i an ramplituderrno'dulaftdf'wave signal,having'a predeterminedA 'carrier frequencyJ luetweenone of said controlgrids and said cathodega circuit from the other, of said control gridsto'said'cathode including a resonant two-terminal load circuit/havingone terminal coupled externally of said device to said other controlgrid only and having an impedance at saidV pref determined frequencygreater than the reciprocal of the, effective transconductance, at saidpredetermined frequen,- cy, of said one control gridwith respect to saidother control grid for developing an amplified signal includingmodulation components of said modulated wavesignal; means coupled tosaid other control gridand said, cathoderfolr effecting separation ofsaid modulation componentsffrom said amplied signal and for applyingsaid separated modulation components to said other control grid tomodulate the electron ow to said output electrode in' accordance withsaidtniodulation components; and means including an output load circuitcoupled to said outputv electrode and to said cathode and utilizing thetransconductance of said other control grid with respect to said outputelectrode for amplifying said modulation com ponents.

2. Wave-signal translating apparatus comprising: an.elect-ron-dischargey device including, in the order named, a cathode, afirstV control grid, an accelerating electrode, a second control grid,and on output electrode; an input circuit for impressing anamplitude-modulated wave-sigl nal, having a predetermined carrierfrequency, between one of said control grids and said cathode; a circuitfrom. the other of said con-trol grids to said cathodeY including aresonant two-terminal load circuit having one termiA nal coupledexternally of said device to said other control i grid only and havingan impedance at said predetermined frequency greater than the reciprocal.of the effective transV conductance, at said predetermined frequency,of said one'V control grid with respect to said other control grid fordeveloping an amplified signal including modulation components of saidmodulated wave-signal; means coupled to. said other control grid andsaid cathode and comprising a rectifier device` included in said circuitfrom said other control grid to said cathode for effecting separation ofsaid modulation components from .said amplified signal and formodulating the electron ow to said output elec trode in accordance with.said modulation components', and means including an output load circuitcoupled to said output electrode` and to said cathode and utilizing thetransconductance of said other control grid with respect to ,said outputelectrode for amplifying said modulation com? ponen-ts. v

3. Wavefsign'al translating apparatus comprising: an electron-dischargedevice including, in the order named, a cathode, a first control grid,an accelerating electrode, a second control grid, and an outputelectrode; an input circuit for impressing an amplitude-modulatedwave-signal, having a predetermined carrier frequency, between .saidfirst control grid and said cathode; a circuit from said second controlgrid to said cathode including a reso? nant two-terminal load circuithaving one terminal coupled extern-ally of said Idevice to said secondcontrol grid only and having an impedance at said predeterminedfrequency greater than the reciprocal of the effective transconductance,at said predetermined frequency, of said first con-V trol grid withrespect to said second control grid yfor de,- velopingan amplifiedsignal including modulation oomponents of said modulated Wave-signal ybyspace charge coupling from said first control grid to said secondvcontrol grid; means coupled to said Isecond control grid and saidcathode for effecting separation of said modulation components from saidamplified signal and for applyingsaid separated modulation components tosaidsecond con trol grid to modulate the electron flow to said -outputelec? trode in accordance with saidmodulation components; and meansincluding an output load circuitvcoupledfto realic Y 11 Y said outputelectrode and to said cathode Iand utilizing the transconductance ofsaid second control grid` with respectV to said output electrode foramplifying said modulation components. t

4. Wave-signal translating apparatus comprising: an electron-dischargeVdevice including, in the order name-d, a cathode, a first control grid,an accelerating electrode, a second control grid, and an outputelectrode; an input circuitior impressing an amplitude-modulatedwave-signal, having arrpredetermined carrier frequency, between saidtirst control grid and said cathode; a circuit from said second controlgrid to said cathode including a resonant two-terminal load circuithaving one Vterminal coupled externally of said device to said secondcontrol grid only and having an impedance at said predeterminedfrequency greater thanthe reciprocal of the effective transconductance,at said predetermined frequency, of said first control grid with respectto said second control grid for developing an ampliiied signal includingmodulation com, ponents of said modulated Vwave-signal; jmeans coupledto said second control grid and said cathode and comprising aunilaterally conductive device included in .said circuit from saidsecond control grid to said cathode for demodulating said amplied signalto provide a detected signal comprising said modulation components andfor modulating the electron ilow to said output electrode in accordancewith said detected signal; and means including an output load circuitcoupled to said output electrode and to said cathode and utilizing thetransconductance of said secon-d control grid with respect to saidoutput electrode for amplifying said detected signal.

5. Wave-signal transl-ating apparatus comprising: an electron-dischargedevi-ce including, in the order named, a cathode. rst control grid, anaccelerating electrode, a second control grid, and an output electrode;an input circuit for impressing an amplitude-modulated wave-signal,having a predetermined carrier frequency, between said first controlgrid and said cathode; a circuit from said second control grid to saidcathode including a resonant two-terminal load circuit having oneterminal coupled externally of said device to said second control gridonly and having an impedance at said predetermined frequency greaterthan the reciprocal of the effective trans conductance, at saidpredetermined frequency, of said first control grid with respect to saidsecond control grid for developing an amplified signal includingmodulation components of said modulated Wave-signal; means coupled tosaid second control grid and said cathode for effecting demodulation ofsaid amplied signal to provide a detected signal comprising saidmodulation components and for applying said detected signal to saidsecond control grid tc modulate the electron flow to said outputelectrode in accordance with said detected signal; means forneutralizing the bilateral interelectrode capacity between said controlgrids; and means including output load circuit coupled to said outputelectrode and to said cathode and utilizing the transconductance of saidsecond control grid with respect to said output electrode for amplifyingsaid detected signal.

Y 6. Wave-signal translating apparatus comprising; an electron-discharge`device including, in the order named, a cathode, a rst control grid, anaccelerating electrode, a second control grid, and an output electrode;an input circuit for impressing an amplitude-modulated Wave-signal,having a predetermined carrier frequency, between .said first controlgrid and said cathode; a circuit from said second control grid to saidcathode including a resonant tivo-terminal load circuit having oneterminal coupled externally of said device to said second control grid.only and having impedance at said predetermined frequency greater thanthe reciprocal of the elective tra-nsconduc-tance, at said predeterminedfrequency, of said `first control grid with respect to said secondcontrol grid for developing am lilied signal including modulationcomponents of said modulated wave-signal; means cou pled to said secondcontrol grid and said cathode for eiecting Ademodulation of saidamplified signal to provide a detected signal comprising said modulationcomponents and for applying said detected signalto said second controlgrid to modulate the electron i'low to said output electrode inaccordance with said detected signal; energy feedmeans coupled betweensaid two-terminal lload circuit and said input circuit for neutralizingthe bilateral interelectrodeY capacity between said control grids; andmeans Vincluding an output load circuit coupled to said output:electrode and to said cathode and utilizing the ,transconductance ofsaid second `control grid with respect to said output electrode foramplifying said detected signal.' Y

7. Wave-signal translating apparatus comprising: an c --discharge deviceincluding, in the order named, a cthode, a rst control grid, anaccelerating electrode, second control grid, and an output electrode; aninput circuit for impressing an amplitude-modulated Wavesignal, having apredetermined carrier frequency, between Ysaid iirst control grid andsaid cathode; a circuit from said second control grid to said cathodeincluding a resonant two-terminal load circuit, comprising an inductor,having one terminal coupled externally of said device torsaid secondcontrol grid only and having an impedance at said predeterminedfrequency greater than the reciprocal of the efiective transconductance,at said predetermined frequency, of said first control grid with respectto said second control grid for developing an amplied signal includingmodulation components ofsaid modulated wavesignal; means coupled to saidsecond control grid and said cathode for effecting demodulation Vof saidamplified signal to comprising said modulation components and forapplying said detected signal to said second control grid to modulatethe electron iiovv to said output electrode in accordance withsaiddetected signal; an energy feedback circuit including a condensercoupled from said inductor to said input circuit for neutralizing thebilateral interelectrodc capacity between said control grids; and meansincluding an output load circuit coupled to said output electrode and tosaid cathode and utilizing the transconductance of said second controlgrid with respect to said output electrode for amplifying said detectedsignal.

8. Wave-signal translating apparatus comprising: an electron-dischargedevice including, in the order named, a cathode, a tirst control grid,an accelerating electrode, a second control grid, and an outputelectrode; an input circuit for impressing an amplitude-modulatedwavesignal, having a predetermined carrier frequency, between said lirstcontrol grid and said cathode; a circuit from said second control gridto said cathode including a resonant two-terminal load circuit havingone terminal coupled externally of said device to Said second controlgrid only and having an impedance at said predetermined frequencygreater vthan the reciprocal of the eiectve transconductance, at saidpredetermined frequency, of said first control grid with respect to saidsecond control grid for developing an amplilied signal includingmodulation components of said modulated Wave-signal; means coupled tosaid second control grid and said cathode, and comprising means includedin said circuit from said second control grid to said cathode, forbiasing ysaid second control grid to a non-linear portion of its dynamictransfer characteristic, whereby sadmodulation corn-V ponents areseparated from said modulated Wave-signal, and for applying saidseparated modulation components to said second control grid to modulatethe electron ow to said output electrode in accordance with saidmodulation components; and means including an output load circuitcoupled to said output electrode and to said cathode and utilizing thetransconductance of said second control grid with respect to said outputelectrode for amplifying said modulation components.

9. 'Wave-signal translating apparatus comprising: yau

provide adetected signal electron-discharge device including, in theorder named, a cathode, a rst control grid, an accelerating electrode, aSecond control grid, and an output electrode; a source of compositetelevision signals, including video-modulated image-carrier andaudio-modulated sound-carrier components separated by a predeterminedfrequency dierence, coupled to said rst control grid and to saidcathode; a resonant two-terminal load circuit having one terminalcoupled externally of said device to said second control grid only andhaving an impedance throughout the frequency hand of said compositetelevision signals greater than the reciprocal of the effectivetransconductance, throughout said frequency band, of said rst controlgrid with respect to said second control grid for developing amplifiedcomposite television signals; means coupled to said second control gridand said cathode for separating said modulation components from saidmodulated wave-signal and for applying said separated modulationcomponents to said second control grid to modulate the electron flow tosaid output electrode in accordance With the modulation components ofsaid amplified signals; and means utilizing the transconductance of saidsecond control grid with respect to said output electrode, including avideo-frequency output load circuit and a second output load circuittuned to an intercarrier frequency corresponding to said frequencydifference, for developing amplied composite video signals and ampliliedaudio-modulated intercarrier-frequency output signals respectively.

10. Wave-signal translating apparatus comprising: an electron-dischargedevice including, in the order named, a cathode, a first control grid,an accelerating electrode, a second control grid, and an outputelectrode; a source of intermediate-frequency composite televisionsignals including video-frequency picture-signal modulation componentscoupled to said rst control grid and to said cathode; a circuit fromsaid second control grid to said cathode including a resonanttwo-terminal intermediatefrequency load circuit having one terminalcoupled externally of said device to said second control grid only fordeveloping an amplified replica of said composite television signals;means coupled to said second control grid and said cathode for eectingseparation of said modulation components from said ampliiied replica andfor applying said separated modulation components to said second controlgrid to modulate the electron ow to said output electrode in accordancewith the videoequency picture-signal components of said amplifiedreplica; and means including a video-frequency output load circuitcoupled to said output electrode and to said cathode and utilizing thetransconductance of said second control grid with respect to said outputelectrode for amplifying said video-frequency picture-signal components.

11. Wave-signal translating apparatus comprising: an electron-dischargedevice including, in the order named, a cathode, a first control grid,an accelerating electrode, a second control grid, and an outputelectrode; a source of composite television signals, includingvideo-modulen ed image-carrier and audio-modulated sound-carriercomponents separated by a predetermined frequency difference, coupled tosaid rst control grid and to said cathode; a resonant two-terminal loadcircuit having one terminal coupled externally of said device to saidsecond control grid only and having an impedance throughout thefrequency band of said composite television signals greater than thereciprocal of the effective transconductance, throughout said frequencyband, of said first control grid with respect to said second controlgrid for developing an amplified signal including said carriercomponents; means coupled to said second control grid and said cathodefor effecting separation of said image-carrier and sound-carriercomponents from said amplified signal and for applying said separatedcomponents to said second control grid to modulate the electron iiow tosaid output electrode in accordance With the intermodulation product ofsaid components corresponding to said predetermined frequencydifference; and means, including an output circuit tuned to anintercarrier frequency corresponding to said predetermined frequencydifference, coupled to said output electrode and to said cathode andutilizing the transconductance of said second control grid with respectto said output electrode for developing an ampliiied audio-modulatedintercarrier-frequency output signal.

12. Wave-signal translating apparatus comprising: an electron-dischargedevice including, in the order named, a cathode, a first control grid,an accelerating electrode, a second control grid, and an outputelectrode; a source of composite television signals, includingvideo-modulated image-carrier and audio-modulated sound-carriercomponents separated by a predetermined frequency difference, coupled tosaid trst control grid and to said cathode; a resonant two-terminal loadcircuit having one terminal coupled externally of said device to saidsecond control grid only and having an impedance at the frequencies ofsaid carrier components greater than the reciprocal of the effectivetransconductance, at such frequencies, of said rst control grid withrespect to said second control grid for developing an amplified signalincluding said carrier components; means coupled to said second controlgrid and to said cathode for biasing said second control grid to anon-linear portion of its dynamic transfer characteristic, whereby saidimage-carrier and sound-carrier components of said amplified signal areseparated from said amplified signal, and for applying said separatedcomponents to said second control grid to modulate the electron ow tosaid output electrode in accordance with the intermodulation product ofsaid components corresponding to said predetermined frequencydifference; and means, including an output circuit tuned to anintercarrier frequency corresponding to said predetermined frequencydifference, coupled to said output electrode and to said cathode andutilizing the transconductance of said second control grid with respectto said output electrode for developing an amplified audio-modulatedintercarrierfrequency output signal.

References Cited in the le of this patent UNITED STATES PATENTS2,165,764 Pitsch July 11, 1939 2,205,243 Dome June 18, 1940 2,248,197Rath July 8, 1941 2,274,184 Bach Feb. 24, 1942 2,532,793 Sziklai Dec. 5,1950 2,547,145 Adler Apr. 3, 1951 2,616,035 Adler Oct. 28, 19522,616,036 Adler Oct. 28, 1952

